Thanks for your inquiry! I'll be happy to provide some product recommendations for you.
Based on the description of your application you will definitely need our
Weatherproof Thermal Transfer material paired with our
Durable Wax/Resin thermal transfer ribbons.
Our Weatherproof Thermal Transfer material consists of a white glossy polypropylene film. It's extremely durable, even in direct contact with water, oil, and various chemicals. The adhesive used for this product is one of our very best - it's graded for excellent adhesion to both smooth and textured surfaces and has a service temperature range of -65°F to 147°F. It should have no problem adhering to your painted wooden stakes.
I looked up the specifications for your printer model and it appears that you will need labels on a 3" core. You can view our 4" x 1" Weatherproof Thermal Transfer product on a 3" core at the link below:
http://www.onlinelabels.com/RL780TW.htmTo achieve the most durable printing results with this material you will need to use our Durable Wax/Resin thermal transfer ribbons. These ribbons provide high resistance to scratching and abrasion, and coupled with the weatherproof material will create printing that is durable to heavy handling, moisture, and chemicals. Datamax printers generally require a Coated Side In (CSI) ribbon type, and I noticed that your printer model calls for a ribbon with a 1" core. The product linked to below should work well for your specific application:
http://www.onlinelabels.com/TR2625RC.htmI hope that you find this information helpful. If you should require any further assistance regarding thermal transfer materials and ribbons please just let me know. I'll be happy to help in any way that I can!